version 0.20.1 fails to build in non-cargo projects

[idobenamram]

Describe the bug
It looks like in rerun 0.20.0-0.20.1 re_build_tools started using cargo metadata. we compile our rust code cargo using bazel (crates universe) which means cargo metadata doesn't work for us. What do you guys suggest we do?

Use --sandbox_debug to see verbose messages from the sandbox and retain the sandbox build root for debugging
Build script process failed with exit code 101
--stdout:
cargo:rerun-if-env-changed=IS_IN_RERUN_WORKSPACE
cargo:rerun-if-env-changed=RERUN_IS_PUBLISHING_CRATES
cargo:rustc-env=RE_BUILD_DATETIME=
cargo:rustc-env=RE_BUILD_GIT_HASH=
cargo:rustc-env=RE_BUILD_GIT_BRANCH=
cargo:rustc-env=RE_BUILD_TARGET_TRIPLE=x86_64-unknown-linux-gnu
cargo:rustc-env=RE_BUILD_RUSTC_VERSION=1.82.0 (f6e511eec 2024-10-15)
cargo:rustc-env=RE_BUILD_LLVM_VERSION=19.1.1
cargo:rustc-env=RE_BUILD_IS_IN_RERUN_WORKSPACE=
cargo:rerun-if-env-changed=IS_IN_RERUN_WORKSPACE
cargo:rerun-if-env-changed=RERUN_IS_PUBLISHING_CRATES

--stderr:
Environment: Not on CI and not in workspace
Environment: Not on CI and not in workspace
thread 'main' panicked at external/_main~rust_crates~crate_index__re_build_tools-0.20.1/src/lib.rs:204:46:
called `Result::unwrap()` on an `Err` value: failed to start `cargo metadata`: No such file or directory (os error 2)

Caused by:
    No such file or directory (os error 2)

Backtrace

Stack backtrace:
   0: <unknown>
   1: <unknown>
   2: <unknown>
   3: <unknown>
   4: <unknown>
   5: <unknown>
   6: <unknown>
   7: <unknown>
   8: <unknown>
   9: __libc_start_main
  10: <unknown>

stack backtrace:
   0:     0x6526fe7ee4fa - <unknown>
   1:     0x6526fe8148cb - <unknown>
   2:     0x6526fe7eb2f3 - <unknown>
   3:     0x6526fe7ef842 - <unknown>
   4:     0x6526fe7ef4ae - <unknown>
   5:     0x6526fe7f00ef - <unknown>
   6:     0x6526fe7efdd7 - <unknown>
   7:     0x6526fe7ee9d9 - <unknown>
   8:     0x6526fe7efa64 - <unknown>
   9:     0x6526fe813393 - <unknown>
  10:     0x6526fe8137c6 - <unknown>
  11:     0x6526fe76ddd1 - <unknown>
  12:     0x6526fe76b793 - <unknown>
  13:     0x6526fe76b789 - <unknown>
  14:     0x6526fe7e6400 - <unknown>
  15:     0x6526fe76b7f5 - <unknown>
  16:     0x77e47162a1ca - <unknown>
  17:     0x77e47162a28b - __libc_start_main
  18:     0x6526fe76b77a - <unknown>

Rerun version
0.20.1

** Additional Context **
Currently we are bypassing the problem by setting the RERUN_IS_PUBLISHING_CRATES flag. But this can easily break in future versions :(

    "re_sdk": [crate.annotation(
        build_script_env = {
            "RERUN_IS_PUBLISHING_CRATES": "1",
        },
    )],
    "re_analytics": [crate.annotation(
        build_script_env = {
            "RERUN_IS_PUBLISHING_CRATES": "1",
        },
    )],
    "rerun": [crate.annotation(
        build_script_env = {
            "RERUN_IS_PUBLISHING_CRATES": "1",
        },
    )],
    "re_video": [crate.annotation(
        build_script_env = {
            "RERUN_IS_PUBLISHING_CRATES": "1",
        },
    )],

[olivewong]

having this as well, also using bazel